In this paper, I examine the background of music theorist Johannes de Grocheio and the circumstances surrounding the production and preservation of his only known treatise, the Ars musice (c. 1275). I survey three institutions in Normandy — the Benedictine monastery at Lessay, the Premonstratensian monastery at Ardenne and the Trinitarian hospice at La Perrine — that Grocheio may have been associated with in his youth. I consider the two monks responsible for preserving his only known treatise: Guy, a monk of Saint-Denis, whose role in this regard is well established, and Johannes de Botis, a monk of the Charterhouse in Cologne, whose role has only now come to light. I then look at Grocheio’s disputed magisterial standing in the university city of Paris and review the evidence for his employment as a teacher in that city. I also focus on Grocheio’s treatment of chant theory, which has received scant attention in the literature compared with his remarks on secular music and his Aristotelian method of describing the subject of music. I contemplate the social context for writing anew on chant theory in a city known for not stipulating music in its arts curricula and reflect on the influence of Aristotle’s writings on Grocheio’s treatment. I end the paper with a survey of the chants that Grocheio names in the Ars musice, confirming that his examination of chant is ‘according to the use of the people of Paris’.